Well, spell casting in general is somewhat weaker in this edition. This is mostly done with the mitigation of Save or Suck spells (many of them have multiple saves or save every round) and a major reduction in stacking (no longer one dispel magic causing the combat to stop for twenty minutes while you recalculate all the bonuses and such). While all full casters in 5e cast like 3.5 sorcerers (wizards can prepare so many levels of spells each day, then choose from this prepared list when expending spell slots at casting time), there are limitations:
1) Wizards no longer have as many spell slots (mitigated by the Arcane recovery feature, which allows wizards to recover a certain levels worth of spell slots once on a short rest, but it does require a short rest).
2) Many spell that are not instantaneous are now Concentration: meaning that the spell could be disrupted by damage, and you can only ever have one concentration spell up at a time.
3) Spells no longer increase in effect with "Caster level": a first level spell cast by an Archmage has the same effect as one cast by an apprentice; you have to use a higher level slot to get more effect, and this 'slot scaling' is rarely efficient (this is somewhat offset by the Save Difficulty increasing with 'caster level'; opponents will find it much more difficult to save against the Archmage's 1st level spell, but he's still only getting 1st level effects out of it) This makes lower level slots more efficient for utility, buff & debuff type spells. Of course, at will damaging cantrips are there to fill the gap; they increase in damage with the caster's level.
4) IMHO high level spell effects are somewhat less than in 3.5; and I'm not referring to damage (which is a poor measure when comparing between editions); you just don't get all the bells and whistles you used to. Summoning spells are sparse and not as prolific; Teleport is higher level; Demiplane is basically Mordenkainen’s Broom Closet; Timestop is not the be all end all it once was.
5) Monsters are generally not as powerful with as many abilities; 5e has gone a long way to reduce the "fiddly bits" and streamline and simplify game play, so you don't necessarily need all the bells and whistles of yesteryear.
1) not sure if it's really mitigated since level 6 spells and above are not affected.
2)this does seem a bit ridiculous to me. i can just imagine high level wizards mind raping low level ones just for the sake of following them around and buffing them up before the battle. besides wizards would use these buffs for the entire party. if anything they helped everyone shine more rather than making the wizard superior
3) generally speaking wizards were always more efficient playing GOD than blasting staff if you ask me.
4) this seems a bit subjective, what does it mean "sparse"? i mean, i assume the total number of spells in the universe is not fixed and more can be researched. after all by definition if it can be thought then magic can do it.
5) i'd call this dumbing down but then again i don't have any experience yet.